Peelably laminated containers are known. These containers are blow molded bottles, generally known as delaminatable bottles, and are obtained by laminating a highly shape-retainable outer layer with an inner layer in the shape of a highly flexible bag in an easily peelable manner.
These blow molded, peelably laminated plastic containers are manufactured by extruding together an outer layer and an inner layer having little compatibility with each other to form a laminated parison, and by blow molding this laminated parison. The bottom seal of the container is obtained by pressing the parison flat and pinching off the tube by means of the pinch-off section of a blow mold. However, since the bottom seal basically has a laminated structure of outer layers and inner layers that have little compatibility with each other, the users as well as the manufacturers were dissatisfied with the way in which the outer layer portions of the bottom are easily cracked.
As a conventional technology used to relieve this dissatisfaction, there is known a technology shown in Patent Document 1, in which a bottom seal mainly comprises a bottom rib. In this case, the bottom seal is formed by pressing a preform tube flat and pinching off the tube by means of the pinch-off section of a blow mold, and the bottom rib is formed in the shape of a ridge along a parting line by laying a pair of rib strips side by side and pressing the rib strips together. In addition, multiple cavities are laterally disposed in the bottom rib in such a way that the rib strip on one side is pushed toward, and caved into, the rib strip on the other side at several points to form cavities, and vice versa.
[Patent Document 1] Japanese patent application No. 1996-216238
As shown in FIGS. 6 and 7, the conventional technology described in Patent Document 1 relates to a blow molded, peelably laminated plastic container 1 comprising a neck 5 at the upper end, a body 4, and a bottom 7 disposed underneath. The bottom seal is formed in the shape of a ridge having some height, and this shape widens the area of the pressure-bonding between the outer layer 2 and the inner layer 3 in the bottom seal 13. In addition, multiple cavities 16 are formed not only to further increase the area of pressure bonding between the outer layer 2 and the inner layer 3, but also to increase the resistance dramatically against the shearing stress working in parallel to the pressed surface, thus making it possible to obtain a bottom seal 13 having high mechanical strength, while making the crack hard to occur.